It very frequently becomes necessary to install an undergroundpipe between two given points such as the opposed sides of a finished driveway or street, for example. It is a routine procedure to provide an operating trench on one side and a target trench on the opposed side, and an installer device is properly positioned in the operating trench.
A first rod length is manually inserted through drive jaw means of the installer device and engaged thereby to push said first rod length under the street, driveway, etc. by a fluid operated cylinder and piston assembly which may be hydraulically or pneumatically operated and which will be hereinafter referred to as pneumatic. The trailing end of the first rod length is provided with a coupling to receive a second rod length and the pneumatic drive means is actuated to push the second rod length forwardly toward the target trench. A sufficient plurality of rod lengths are similarly attached to preceding rod lengths until the leading tip end of the first rod length emerges into the target trench.
The leading tip end is threadedly provided with a pusher cap which is then removed and replaced with an adapter for attachment to an end of a pipe to be permanently installed under the above surface. For this purpose, the direction of movement is reversed to pull the rods with the pipe attached thereto back through the hole, formed by the rod, until the leading end of the pipe emerges into the operating trench.
The above described operations are quite conventional, however, one particular difficulty is frequently encountered with the use of drive jaws heretofore used to drive the rods through the ground. Large underground rocks are frequently encountered which generally crumble or crack apart to permit passage therethrough of the rods because of the tremendous forces applied thereto by the drive means. However, in extreme cases, the rods which are generally of solid steel will bend between the drive jaws and guide means. Operations must then be suspended until the bent rod is removed and replaced. This is time consuming and also costly as the bent steel rod is then discarded.
Heretofore, the jaws utilized to engage and drive the rods during the hole forming operation are pivoted on transverse axes substantially out of transverse alignment with the longitudinal axis of the coupled hole forming rods. When a very substantial resistance is encountered during the hole forming operation, such as an encounter with a large solid rock, the actual drive forces provided by the fluid drive means will continue to move the jaws forwardly, however, under severe conditions, the off center pivotal arrangement of the drive jaws relative to the rod axis results in a substantial bend in the rod.
The structure of the present invention provides pivot means for the drive jaws with a common axis thereof extending transversely through the longitudinal axis of a rod engaged through the drive jaws. Therefore, when very substantial forces are applied to the drive jaws by a pneumatic drive means, said forces are imparted to the pivot means in a transverse centered relation to the longitudinal axis of the rod in contrast with the substantial off centered relationship between the pivot means and rod axis of prior art devices, and the axially centered forces permit the rods to break through rock obstructions without bending.
Therefore, one of the principal objects of the present invention is to provide an underground pipe installer device with reciprocably operable drive jaw means, including pivot means in a continuous, transverse, intersecting relation to the longitudinal axis of a hole forming rod assembly operably engaged in the drive jaw means for selective movement by appropriate drive means in a forward hole forming direction, and in a return direction for positioning a pipe in the formed holes.
A further object of the invention is to provide bronze slide blade bearing means for the drive jaw means in longitudinal slots in a side wall structure of the pipe installer device.